Stoney Gate Valve Replacement

Project Summary

The Stoney Gate Valve Replacment project for the U.S. Army Corps of Engineers (USACE) replaced the original large lock chambers’ 100-year-old filling culvert gates at the Hiram M. Chittenden Locks, also known as Ballard Locks. IMCO replaced the large lock center gate bushings and gudgeon pin, components that support the weight of the gates, allowing them to rotate open and closed.

The existing gate valves were over 105 years old and original to the structure. The project team performed demolition and removal and replacement of the existing stoney gate valves, and installed new hydraulic power systems and operating machinery. The stoney gate valve system consisted of six gate valves that control the filling and emptying of the ship canal large lock chambers on Lake Washington. The valves are located in culverts 14 by 8.5 feet wide and were only accessible when the large lock chambers were dewatered by the government. This work was spread out over three separate dewatering events.

The Ballard Locks are the busiest lock and dam facility in the United States, measured by number of vessels. Through collaboration with USACE and our subcontractors and suppliers, IMCO was able to expedite delivery of the materials for timely installation with the project re-sequencing and successfully eliminate the need for a final lock closure. Deleting the fourth dewatering closure minimized impacts on the community, making boaters and local business owners happy and allowing them to freely move between Puget Sound, Lake Union, and Lake Washington.



Seattle, Washington


United States Army Corps of Engineers

Contract Amount

$10.5 million


September 2018 - April 2021

Project Highlights

The original project specifications called for four 45-day dewatering closures, significantly impacting the local maritime community and stakeholders. IMCO proposed a revised construction sequence to eliminate one of the outages as a no-cost change.